Electronic trigger and switch circuits



Dec. 19, 1950 c. E. CLEETON 2,534,233

ELECTRONIC TRIGGER AND SWITCH CIRCUITS Original Filed Jan. 24, 1940 2 Sheets-Sheet 1 as 82 75 7o 78 e3 e0 59 I 54 55 I 40 46 8 5| 52 A (5O 45 I Q 49 :'l 6 61 :I; l-

INVENTOR.

' CLAUD E. CLEETON ATTORNEY Dec. 19, 1950 c. E. CLEETON 2,534,233

ELECTRONIC TRIGGER AND SWITCH CIRCUITS Original Filed Jan. 24, 1940 2 Sheets-Sheet 2 IIo I08 I06 II? I2I I25 I09 I (I03 H8 1 H22 l 90 L 9| n4 7 I02 H6 3 Ill |24r Ll aw [Cl 92 93 H5 I28 95 96 I29 II2 I25 98 I00 PLATE POTENTIAL sgz o NS ANT GRID POTENTIAL LII INVENTOR. CLAUD E. CLEETON ATTORNEY cuit;

Patented Dec. 19, 1950 ELECTRONIC TRIGGER AND SWITCH CIRCUITS Claud E. Cleeton, Washington, D. 0.

Original application January 24, 1940, Serial No. 315,340. Divided and this application August 13, 1948, Serial No. 44,211

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 8 Claims.

My invention relates generally to switching devices utilizing vacuum tubes, and particularly to such devices having trigger circuits for setting them into operation. It also relates generally to electronic devices for controlling associated circuits, and in particular to selflocking electronic relays, electronic counters, pulse expanders and square wave generators, and is a division of my application Serial No. 315,3i0, filed January 24, 1949. My invention will be described in connection with the following drawings, in which,

Fig. 1 shows schematically the basic circuit of my invention, including the electronic trigger circuit;

Fig. 2 is a schematic diagram of the trigger circuit adapted to serve as an electronic self-locking relay with electrical reset, in which an electromechanical relay may be controlled or a two circuit amplifier may be switched;

Fig. 3 is a schematicdiagram using one pair of tubes in a two circuit amplifier switching cir- Fig. 4 shows a pair of curves indicating the relation between the grid potential applied to a trigger circuit and the resulting plate potential; and

my invention. The cathodes H, E2 of both tubes are connected to ground. Grids l3 and M are grounded through grid leak I 5, and both connect to terminal |B through capacitor H. The screen grids 8, IQ of both tubes are connected to the positive terminal 29 of a screen grid supply source.

Grids 2| and 22 are shielded by screen grids l8 and I9 respectively. Grid 2| of tube 9 is connected to the negative terminal 24 of the direct potential grid supply source through grid resistance 23 and is also connected to the anode 25 of the opposite tube Iii through a circuit comprising resistance 26 and capacitance 27 in parallel. Grid 22 of tube it is cormected to terminal 24 through grid resistance 29 and is also connected to the anode 29 of the opposite tube 9 through a circuit comprising resistance 39 and capacitance 3| in parallel. Both anodes25 and 29 are connected to the positive terminal 32 of an anode direct potential supply source, anode 25 through resistance 34 and anode 29 through anode resistance 33. Terminal 35 is connected to anode 25 of tube ||l through capacitance 36. Grid 3! of tube 9 and grid 3.8 of tube i ii are shown internally connected to cathodes of their respective tubes.

Fig. 5 is the typical working diagram for the The negative terminals of both the screen grid and the anode supply sources are connected to ground, as is the positive terminal of the grid supply source. Obviously, the same source may be employed to energize the entire circuit shown provided proper polarities are observed and appropriate voltage employed. The negative potential applied to grids 2|, 22 by the source connected to terminal 24 is of such value that, if it were the only voltage applied to these grids, each tube would be biased considerably past cutoif. However, it will be noted that, in addition to the aforementioned negative potential, a positive potential is applied to each grid 2|, 22 from the anode of the opposite tube. This positive potential varies in value depending upon the conductivity state of such opposite tube, i. e., when no anode current flows in tube 9, the positive potential applied to grid 22 of tube Iii from the anode 29 of tube 9 is of such value that the resultant potential of grid 22 is approximately zero. Similarly, when no anode current flows in tube Hi, the resultant potential of grid 2| of tube 9 is approximately zero.

With the cathodes of tubes 9 and Ill heated in a conventional manner, when the supply voltages are applied to terminals 29, 24 and 32, shock excitation causes anode current to flow in one of tubes 9, l0, say tube 9. Due to the small circuit unbalance inevitably present, anode current does not begin to flow in both tubes simultaneously. This flow of anode current in tube 9 causes a volt-' age drop in anode resistance 33 with consequent reduction in the positive potential at anode 29 of tube 9 and at grid 22 of tube Ill. The result of this reduction in the positive potential applied to grid 22 is that grid 22 becomes negative and anode current is prevented from flowing in tube In. With no anode current flowing in tube it, there is applied to anode 25 almost the full potential of terminal 32 and a correspondingly high positive potential is applied to grid 2| of tube 9, such that the resultant voltage of grid 2| is approximately zero, and anode current continues to flow in tube 9.

If now a negative pulse is applied to grids l3 and M through capacitance ll, the anode current of tube 9 will be reduced. This reduction in the anode current of tube 9 results ina smaller potential drop in anode resistance 33 and also in an increased positive potential being applied flow of anode current through anode resistance ing negative pulse will again reversethe 'conductivity state of the tubes, and thus restore the circuit to its original condition, i.'e., with tube 9 conductive and tube it non-conductive.

It will be noted that there are only two stable states of anode current in the above circuit,'that is, anode current flowing in one tubeand zero in the other, and vice versa When tubeil jor Ill is non-conductive the value of the resultant'voltage appliedto their respective grids2 l, 22 is such as? to prevent plate current from beginning to flow "infthe non-conductive tube when a positive pulse is applied to grid l3 or I4, as the case may be. {A positive pulse applied to grid i3 or M of the "conductive tube will obviously cause no changefoveror reversal of the conductive state of the ftubes. Thus, itis only when'a negative pulse is applied to grid 13 or [4 of the conductive tube that the reversal occurs.

fThe icircuit including capacitance 36 and terfn ii al'as may be utilized'to couple to an external circuit the voltage variation of anode of tube I0, I The circuit as well as the tubes of Fig. 1 are fsaid to be triggered when negative pulses applied "thereto cause a reversal in the conductive fst'ate of the'tubes. The tubes and circuit are ftriggered by applying the negative pulses to ids l3 and I4, each such grid being a part of ftvhfat is, in effect, a triode, the elements of one such triodebeing grid |3, cathode H and screen f'grid l8; the elements of the other triode being grid l4, cathode l2 and screen grid l9. Tubes 9 and in are coupled through circuit means including'the anodes thereof and grids 2| and 22.

, Used'as'an electronic relay, the apparatus 'of 1 is described as being set or re-setwhen tube 9' is conductive and as being tripped when "tube I] is conductive.

Electromechanical relays can be inserted in tl' e anode circuit of either or both tubes, such relays being actuated by the flow of anode current.

Variations in the circuit of Fig. 1 'make it adaptable for use in connection with other cir- 1cuits, as shown in the subsequent figures. In Fig.

2,'m'ulti grid tubes 39 and 4|! are shown with their cathodes and 42 connected to ground, with grid 43 of tube 39 grounded through grid leak "'44 and connected to terminal 45 through capaci- "ta'nce 46, and with grid 41 of tube 40 grounded through grid leak 48 and connected toterminal ,49 through capacitance 50. Screen grids 5| and 52 of tubes 39 and 49 respectively, are connected to the same positive terminal 53 of a screengrid supply source, while -grids '54 and 55 are shown connected to the cathodes of their respective tubes. Grid 56 of tube 39 is connected to the negative terminal 5'! of a grid supply source through. grid resistance 58 and is also connected "to plate 60 of tube as through a circuit comprishing resistance 69' and a capacitance 6| in parallel. Grid 6| of tube 40 is connected to terminal 51 through gridresistan'ce 62 and is further connected to emcee; of tube 39 through'a cir- "Lc'u'it' comprising resistance 64 ana'eapaeitanee 65 in parallel. Both anodes B0 and 63 connect to the same positive terminal 66 of an anode supply source, anode Go through anode resistance 6?, and anode fi3througli resistance 58. Electronic tubes 69 and "it are amplifier tubes of any type having at least one anode, a grid and a Grid ll of tube 69 is connected to grid 58 of tube through coupling resistance i2 and to input terminal 13 through capacitance l4.

Grid 15 of tube iilisconnected to the grid 6| of tube ll) through coupling resistance 16 and to input terminal ll through capacitance l8. Cathode l5 "of tube 69andcathode 86 of tube 79 are both impedance 85. Anode 8| is'connected to output "terminal 86 through capacitance Bl while anode 82 connects tooutput terminal 88 through cafpaoitance 89. The negative terminals of the supfplysources connected to terminals 53, 56 and 83 25' terminal ,of the grid supply source connected to terminal 5? is likewise grounded. As in Fig. l,

are all connected to groundfwhile the positive the same'source may be utilized to energize ter- 'mi nals 5 3, 51, 66 and 83, provided proper polarities are observed and proper potentials utilized.

Thecircuit of Fig.2 operates'as follows: When the supply potentials are applied to terminals 53, 5], 66 and 83, the circuit including tubes 39 and will assume one of the stable conditions described in Fig. l, that is, with one tube conductive and with no anodejcurrent flowing in the other. Suppose in the particular stable conditionassumed by the circuit, tube 39 is conduc- "tive. 1A fnegativ'epulse then applied'to grid 43 0 -of tube 39 through capacitance '46 will produce a reversal or change-over, in the manner described inthe explanation of Fig. l,'and tube 40 willnow be conductive "with tube 39 non-conductive. Additional negative pulses applied to grid 43 will produce no effect on the plate'c urrent of either tube, nor'will positive pulses applied to this grid be able to cause a flow'of plate current in tube To cause a reversal or change-over it will now"be"nec'essary to apply a negative pulse to "gridf ll of tube 40 through capacitance Thus, "the reversal is obtained by applying a negative pulse to grid 43 or 41,

as the case may be, of thepartic'ular tube which may be conductive at the'time.

Grid H of tube 69 has the same potential with respect to its cathode l9, and hence with respect to ground, as has grid 56 ofjtube' 39. 'Also, grid T5 of tube 10 has the same potential with respect to its cathode and hence with 'respect to "ground, as grid 9| of tube 59. This being so,

when tube 39 is conductive and tube 43 non- 'conductive, one of the two stable states of the circuit, the potential of grid 56 lof'tube 39 and of grid H of tube 59 is approximately zero and 65 tube 69 will amplify voltages applied to grid H throughcapacitance 14, such amplified voltage appearing at terminal 86. At the same time, the potential of grid 6| of tube 40 and also of grid 15 of tube 10 being fnega'tive'with respect to its cathode, no plate current'will flow in tube and no output voltage will appear at terminal 88 when, voltages are applied 'to' grid 15 through capacitance 18. If a negative pulse is applied to grid 43 of tube 39, areversal of the conductive state of tubes 39 'and4ll'will occur as previously described, and tube 39 now becomes non-conductive with tube 40 conductive. When this occurs, tube 69 will block voltages applied to its grid H while tube 70 will amplify voltages applied to grid I5, the amplified output of tube appearing at terminal 88. If then a negative pulse be applied to grid 4'! of tube 49, such will cause a reversal of the conductive state of tubes 39 and 49 and a consequent reversal in the amplifying state of tubes 99 and I0. This process of switching the amplifier tubes from an amplifying to a non-amplifying state, and vice versa, may be continued by applying negative pulse alternately to grids 43 and 41. Through the connections including resistances l2 and I6, amplifier tubes 69 and it are thus so coupled to tubes 39 and 40, respectively, as to be controlled thereby.

In Fig. 3, in which the trigger circuits, amplifier switching circuits and amplifier circuits are combined in a, single pair of tubes 99' and 9|, which are preferably of the type known as the 6A8, but other pentagrid of pentode tubes will operate successfully in the circuit shown. In this figure, grids 92 and 93 are connected to a common terminal 94 to which the negative terminal of a grid supply source is applied, grid 92 through grid resistance 95 and grid 99 through grid resistance 96. Grid 92 is also connected to terminal 91 through capacitance 99 while grid 93 is connected to terminal 99 through capacitance I00. Grid |0| of tube 99 is connected to screen grid I02 of this same tube and both grids |9| and I92 are connected to grid 93 of tube 9| through a circuit comprising capacitance I03 and resistance IM in parallel. Grids |9| and I92 are further connected to terminal I95 through screen grid resistance I96. The positive terminal of a common anode and screen grid supply source is applied to terminal E95. Anode E9? of tube 99 is connected to terminal I95 through anode resistance I08 and also to output terminal I09 through capacitance II9. Grid III is connected to ground through grid leak H2 and is also connected to input terminal H3 through capacitance Il l. Grid H5 and screen grid IIIi of tube 9| are both connected to terminal I95 through screen grid resistance II! and are also connected to grid 92 of the other tube 99 through a circuit comprising capacitance IIB and resistance H9 in parallel. Anode I connects to terminal I95 through anode resistance |2| and to output terminal I22 through capacitance I23. Grid I24 is connected to ground through grid leak I25 and is also connected to input terminal I29 through capacitance I21. Both cathodes, l29 of tube 90 and I29 of tube 9|, are grounded. In this circuit, the coupling between tubes, which is necessary for the reversal of conductivity of the tubes responsive to triggering pulses, is between grid 92 of tube 90 and grids H5 and H6 of tube 9!, and also between grid 93 of tube 9| and grids I05 and I02 of tube 99. A grid supply source is connected between terminal 94 and ground, the negative terminal of such grid supply source being connected to terminal 99. If desired, all the above supply potentials may be supplied from a single source.

In operation, anode and screen current will begin to flow first in one tube, say tube 99, when the supply voltages are applied, the flow of current to grid I 9| and screen grid I92 through resistance I06 causing a voltage drop in resistance W6 and a reduction in the positive potential applied to grid IIII and screen grid I92. This same positive potential is likewise applied to grid 93 of the opposite tube 9| through resistance I04. A nega-- tive potential is also applied to grid 93 from terminal 94 through resistance 99 of such value that when tube 99 is not conductive, and hence with no current flow to grid IUI and screen grid I02 and no voltage drop in resistance I96, the resultant potential of grid 93 is approximately zero. Thus, when grid SM and screen grid I02 draw current with consequent reduction in the positive potential applied to grid 93, grid 93 becomes negative and tube 9| remains non-conductive, with neither of its anode I20 nor its grid i I5 nor screen grid IIG .drawing current. With no current flow through resistance I I1, the positive potential applied to grid 92 of tube 99 through resistance 9 is of such value that the resultant potential of grid 92 is approximately zero, and tube will remain conductive.

If now, a negative pulse be applied to terminal 91, and hence to grid 92 of tube 99 through capacitance 98, the current flow to grid HM and screen grid I02 will decrease, and the positive potential applied to these grids and also to grid 93 of tube 9| will increase sufficiently that grid H5 and screen grid II6 of tube 9| will begin to draw current. Such will cause a decrease in the positive potential applied to grids H5 and HE due to the voltage drop in resistance In, the resultant voltage of grid 92 of tube 99 will become negative, the current drawn by grid II and screen grid I02 will be further decreased, until tube 90 reaches a stable non-conductive state with tube 9| conductive. If now a negative pulse be applied to grid 93 of tube 9|, such will cause a reversal in the conductive state of the tubes in a similar manner.

Similarly, with tube 90 non-conductive, and tube 9| conductive, a positive pulse applied to grid 92 through capacitance 98 will cause a reversal, due to the great controlling effect of grid 92 on the current drawn by screen grid I02 and grid IOI. This positive pulse will cause grid I9I and screen grid I02 to draw current, which current flowing through resistance I06 causes a reduction in the positive potential applied to grid 93 of tube 9|, such that the resultant potential of grid 93 will be negative. This in turn will cause a reduction in the current to grids I I5 and H6, a reduced potential drop in resistance II! and an increase in the positive potential applied to grid 92, such that tube 99 will then become conductive and tube 9| non-conductive. In a like manner, if tube 99 is conductive and tube 9| non-conductive, a positive pulse applied to grid 93 of tube 9| through capacitance I99 will pro-- duce a reversal or change-over in the conductive state of the tubes. When tube 99 is conductive, voltages applied to terminal H3 and hence to grid III through capacitance l will be amplified by this tube, the amplified output voltage appearing at terminal I09. When tube 99 is non-conductive, voltage applied to terminal I i3 will produce no output at terminal I99. Similarly, when tube 9| is conductive, it will ampiiiy voltages applied to terminal I26 and hence to grid I24 through capacitance I21, the amplified output voltage appears at terminal I22; when tube 9| is non-conductive, it will block voltages applied to terminal I26.

By connecting together terminals 3 and I29.

in Fig. l.

'ouit =less critical to voltage variations. cults shown and described herein. are not critical multi-grid tubes forcontrelling else relays connected in"the anode circuits tubes as described underFigs; 1, 2 and 3'or switching amplifier tubes lay-controllingthe-bia and as (Fig. 2) er terminals m9- and I22 (Fig.3) the circuit of either'Fig. 2 or Fig. 3 can be used applied to the triggering grid and the resulting plate'voltage of one relay tube of a circuit such 'as that shown in Fig. -l, plotted as a function of time. The plate voltage of the other relay tube 180 out of phase with the plate voltage shown This'figure shows how a short pulse applied to the'grid of the tripping tubes will produce a square wave output in the plate circuit; at one-half the frequency.

The curve of Fig. 5 is plottedwith anode "supply terminal voltage as abscissae and with 'grid supply terminal voltage as ordinatesand shows a typical working area for the type of 'circuitdescribed, the screen grid supply terminal voltage remaining constant. Points within the closed curve givevoltage conditions under which the circuit will operate, points on the'curve give voltages at which the circuit beginsto' fail'and points outside the curve show voltage conditions under which the circuit is inoperative. It is'apgrid, and screen grid for afplate, none of whose elements are used for the coupling between tubes which is essential to set up the circuit having the two stable states which may be triggeredirom one to another. The resulting circuit is nore satisfactor thanother known circuits in that the operating range, as measured by curves such as shown in Fig. '5, is larger, thereby having a cir- The cirto the'wave form'of the input voltage.

The-following specific values of constant have been found suitable for the c.':cuit cf Fig. l. Corresponding values will be" found satisfactory in the other circuits shown. It is to be emphasized that I do not-limit myself to the specific values of constants but merely include them herein'as some suggested values-which have been found to be satisfactory.

In Fig. 1, resistances 33 and t i may be about pacitanoe l7 maybe small, its value depei "1gp.

upon the formoithe input pulse. Inthis ea figure, the voltage between terminaltfl and the tube cathodesmay be from l00- to lvolts; the voltage between terminalEU-andie tube cathodes maybe frornG to volts; the voltage be- 'tween-terminali i and-the tube cathodes niaybe from 40 to 100 volts. I

" New uses for the trigger circuits describedh ein include: A self-locking electr thereof (Fig. 2).

* A'"tri'g'ger circuit using mu ti grid -tubes for the-purpose of expanding-a pulse'into asquare wave (illustrated graphically in Fig.4)

A trigger circuit using multi-grid-tubes for-the purpose of generating a-square wave voltage from 'asine wave source'of' much loweramplitude,

A trigger circuit using mu'lti grid-tubesfor the "purpose of frequency dividing or in electronic counter circuits,

Other modifications and changes in the numher and arrangement of the parts maybe made by those skilled in the art without departing from the nature of the invention, within the scope of what is hereinafter claimed.

The invention described herein may be manufactured and/or used by or for the Government of this invention-what is claimed is:

1. In combination, a first multi-grid electron tube and a-second multi-grid electron tube each having a cathode element, a first grid element,

a second grid element, a screen grid element and an-anode element, and two amplifier electronic tubes, each having a cathode, a grid and an anode, a common connection for said cathodes "and said cathode eiementaa common anode supply means and a respective anode resistanceconnesting said anode element to said supply means, acommon screen grid-"supply means-and means connecting each said screen grid element tosaid screen grid supply means, a resistance and a capacitance in parallel connecting said se'cond grid of said second multi-grid tube to saidanode ele- "ment of said first multi-grid tube, a resistance ing a respective grid resistance connecting each said second grid element to said grid supply means, said mul'ti-grid tubes being alternately conductive,"whereby a negative pulse applied to the first grid element of said conductive multigrid tube reverses theconductivitystate of said multi-grid tubes, a coupling resistance connecting the grid of one said amplifier tube to the second grid element of said'first multi-grid tube, a cou pling resistance connecting the gridof said'other amplifier tube to the second grid element'of said sec0nd multi-grid tube, whereby the potential of the said second grid element of each said multigrid tube is respectively applied to the grid of said amplifier tube to which such second-grid is-connested, whereby each said amplifier tube-is coupled a different said'multigrid tube,- a common plate supply means'and a separate plate impedance"ccnne'ctingeach said anode to said-plate supply means, and an input means and ancutput means for each said amplifier tube, whereby each said amplifier tube is-in an amplifying state when the multi-gridtube to which it is coupled is in a conductive state, said amplifier tubes being in an amplifying state alternately.

2. In combination, two multi-grid electron tubes each having a cathode element, a first grid element, a second grid element, a-screen grid element and an anode element; separate means for triggering each said multi-grid tube including the means for coupling said multi-grid tubes including said second grid elements and said anode elements, supply means for energizing elements including a means for increasing the potential drop to said anode elements, whereby said multi-grid tubes are alternately made conductive, a negative pulse applied to the first grid element of each said multi-grid tube when conductive reversing the conductivity state of said multi-grid tubes, two amplifier tubes each having a cathode, a grid and an anode, means directly connecting and coupling the grid of each said amplifier tube to a separate second grid element, whereby each said amplifier tube is coupled to a different said multigrid tube, a plate supply means and a respective plate impedance connecting each anode to said plate supply means, an input means and an output means for each said amplifier tube, each said grid having applied thereto the voltage of the second grid element to which connected, each said amplifier tube being in an amplifying state when the multi-grid tube to which it is coupled is in a conductive state.

3. In combination, an electronic relay means including two multi-grid electron tubes operative to have two stable states said multi-grid tubes responsive to negative pulses for reversing the conductivity state of said tubes, an amplifying means including two other electron tubes and means controlling said amplifying means comprising a control grid in each of said other electron tubes, and means directly connecting and coupling each of said control grids to a grid of a respective one of said multi-grid electron tubes.

4. In combination, an electronic relay means including two multi-grid electron tubes operative to have two stable states said multi-grid tubes responsive to negative pulses for reversing the conductivity state of said tubes, said multi-grid tubes being alternately conductive, and amplifying means including two other electron tubes, means establishing control of each of said other tubes by :a separate one of said multi-grid tubes, said means comprising a control grid in each of said other tubes and means directly connecting and coupling each of said control grids to a grid of a respective one of said multi-grid tubes, whereby each of said other tubes will be in an amplifying state when the multi-grid tube controlling it is in a conductive state.

5. In combination, an electronic relay means including two multi-grid electron tubes operative to have two stable states said multi-grid tubes responsive to negative pulses for reversing the conductivity state of said tubes, an amplifying means including two other electron tubes, and an input means and an output means for each said amplifying means, and means coupling each of said input means to a respective one of said multigrid tubes, thereby establishing control of a said amplifying means by said relay means.

6. In combination, an electronic relay means including two multi-grid electron tubes operative to have two stable states said multi-grid tubes responsive to negative pulses for reversing the conductivity state of said tubes, said multi-grid tubes being alternately conductive, amplifying means including two other electron tubes, each said other tube being controlled by a separate said multi-grid tube, each said amplifying means being in an amplifying state when the multi-grid tube controlling it is in a. conductive state, and an input means and an output means for each 10 said amplifying means, each of said input means being directly connected and coupled to a grid of zine of said multi-grid tubes to provide said conrol.

7. In combination, two multi-grid tubes each having a cathode, a first grid, a second grid, a screen grid and an anode, a common connection for said cathodes, a common grid supply means and means including a respective grid resistance connecting each said first grid to said grid supply means, a resistance and a capacitance in parallel connecting the said first grid of each said tube to the said screen grid of the other said tube, a common anode and screen grid supply means, a separate resistance connecting each said screen grid and each said anode to said common supply means, separate means to apply a negative potential to said second grids, said second grid of each said tube being screened b the said screen grid thereof, separate input means connected to each said second grid, and a separate output means connected to each said anode, whereby the potential applied to the screen grid of each said tube is applied to the first grid of the other said tube, said tubes being alternately conductive, whereby a negative pulse applied to the first grid of each said tube when conductive or a positive pulse applied to the first grid of each said tube when non-conductive reverses the conductivity state of said tubes, each said tube when conductive amplifying voltages applied to the said input means thereof.

8. In combination, two multi-grid tubes each having a cathode, a first grid, a second grid, a screen grid and an anode, a common connection for said cathodes, a common grid supply means and means including a respective grid resistance connecting each said first grid to said grid supply means, a resistance and a capacitance in parallel connecting the said first grid of each said tube to the said screen grid of the other said tube, a common anode and screen grid supply means, a separate resistance connecting each said screen grid and each said anode to said common supply means, separate means to apply a negative potential to said second grids, separate input means connected to each said second grid, and a separate output means connected to each said anode, whereby the potential applied to the screen grid of each said tube is applied to the first grid of the other said tube, said tubes being alternately conductive, whereby a negative pulse applied to the first grid of each said tube when conductive or a positive pulse applied to the first grid of each said tube when non-conductive reverses the conductivity state of said tubes, each said tube when conductive amplifying voltages applied to the said input means thereof.

CLAUD E. CLEETON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS et al., line 19 on page 174 through line 2 on page 1'76, first published in July 1942. 

